End-to-End Operating Mode

TM 11-6625-922-15

(1) RECEIVE IMPEDANCE Ω switch to proper

modulation, and 4 milliseconds for 250 Hz modulation.

impedance.

3-4. End-to-End Operating Mode

(2) % MOD-RECEIVE LEVEL-TRANSMIT

LEVEL switch to RECEIVE LEVEL.

To perform a transmission line delay

(3) RECEIVE LEVEL DBM switch to obtain a

reading on the dbm/% MODULATION meter between 0

measurement using the end-to-end mode, use a TS-

DB and -10 DB.

2669/GCM at the input to the line and a separate TS-

(4) MODULATION FREQUENCY HZ switch to

2669/GCM at the output of the line (fig. 3-3). Allow a

250.

30-minute warmup period for both units. A modulated

(5) DELAY AMETER RANGE MS switch to .15-

carrier produced by the transmitting TS-2669/GCM is

.5.

sent down the line. At the receiving end of the line, a

(6) COARSE DELAY MS and FINE DELAY MIS

reference signal generated by the receiving TS-

switches to obtain an onscale reading on the DELAY

2669/GCM is adjusted to synchronize with the

meter.

modulating frequency of the received signal. This is

(7) The DELAY meter indication will oscillate

usually done with a transmitted carrier signal in the

backs and forth slowly. Adjust the MOD FREQ ADJ

frequency range of anticipated minimum delay of the

control slowly until the DELAY meter indication is stable.

line under test. The carrier frequency of the transmitting

Now both the transmitting and receiving TS-2669/GCM's

TS-2669/GCM is then varied over the pass band of the

are synchronized.

transmission system while noting the variation in line

(8) Momentarily depress the SYNC pushbutton.

output level and delay at the receiving TS-2669/GCM.

The DELAY meter indication will now deflect to the

extreme left of scale.

b. Using the measurement setup of figure 3-3,

(9) Operate the COARSE DELAY MS and FINE

operate the controls and switches on the transmitting

DELAY MS switches to their 0 positions and adjust the

TS-2669/GCM as follows:

DELAY ZERO ADJ control to obtain a zero reading on

the DELAY meter.

(1) POWER switch to ON.

(2) REF RETURN-END TO END switch to END

d. Measurements of delay may now be obtained by

TO END.

operating the MODULATION FREQUENCY HZ switch

(3) % MOD - RECEIVE LEVEL-TRANSMIT

to the desired modulation frequency on both the

LEVEL switch to % MOD.

transmitting and receiving TS-2669/GCM's. Operate the

(4) MODULATION FREQUENCY HZ switch to

SWEEP-CARRIER-REFERENCE

switch

the

250.

transmitting TS-2669/GCM to CARRIER. The line

(5) Adjust % MOD ADJ control to obtain 45- to

carrier frequency may now be adjusted by the CARRIER

50-percent reading on dbm/% MODULATION meter.

FREQUENCY control on the transmitting TS-

(6) % MOD - RECEIVE LEVEL-TRANSMIIT

2669/GCM.

LEVEL switch to TRANSMIT LEVEL.

(7)

TRANSMIT

FREQUENCY-RECEIVE

e. A random check of the stability of the modulation

FREQUENCY switch to TRANSMIT FREQUENCY.

frequency oscillators in both transmitting and receiving

(8) SWEEP - CARRIER - REFERENCE switch

TS-2669/GCM's can be made by operating the SWEEP-

to REFERENCE.

CARRIER-REFERENCE control on the transmitting unit

(9) TRANSMIT LEVEL DBM switch to proper

to REFERENCE and noting the delay reading at a fixed

output signal range.

frequency.

Since the REFERENCE FREQUENCY

(10) TRANSMIT LEVEL DBM control to exact

control is not used during a measurement, it always

output level.

remains set to the same frequency; therefore, at any

(11) COUNTING TIME switch to 1 SEC.

(12) TRANSMIT IMPEDANCE Ω switch to

time during a measurement the operator can switch to

the reference frequency to see that the delay reading at

proper impedance.

this frequency has not changed. If change indicates a

(13) MOD FREQ ADJ control fully ccw and then

drift in one of the master oscillators it can be corrected

5 turns cw.

by repeating the synchronization procedure.

(14) REFERENCE FREQUENCY control to

f. The lowest possible modulation frequency should

middle of measurement band (at least 1 kHz).

be used during the measurements as the drift rate is

directly proportional to the modulation frequency.

Operate the controls and switches on the

receiving TS-2669/GCM as follows:

g. An absolute measurement of line delay cannot

be made using end-to-end operation. Only the relative

3-9